<?php

/**
 * @file
 * SQL date functions.
 */

/**
 *  A helper function to do cross-database concatation of date parts
 *
 *  @param $array - an array of values to be concatonated in sql
 *  @return - correct sql string for database type
 */
function date_sql_concat($array) {
    global $db_type;
    switch ($db_type) {
        case ('mysql'):
        case ('mysqli'):
            return "CONCAT(" . implode(",", $array) . ")";
        case ('pgsql'):
            return implode(" || ", $array);
    }
}

/**
 * Helper function to do cross-database NULL replacements
 *
 * @param an array of values to test for NULL values
 * @return SQL statement to return the first non-NULL value in the list.
 */
function date_sql_coalesce($array) {
    global $db_type;
    switch ($db_type) {
        case ('mysql'):
        case ('mysqli'):
        case ('pgsql'):
            return "COALESCE(" . implode(',', $array) . ")";
    }
}

/**
 *  A helper function to do cross-database padding of date parts
 *
 *  @param $str - a string to apply padding to
 *  @param $size - the size the final string should be
 *  @param $pad - the value to pad the string with
 *  @param $side - the side of the string to pad
 */
function date_sql_pad($str, $size = 2, $pad = '0', $side = 'l') {
    switch ($side) {
        case ('r'):
            return "RPAD($str, $size, '$pad')";
        default:
            return "LPAD($str, $size, '$pad')";
    }
}

/**
 * A class to manipulate date SQL.
 */
class date_sql_handler {

    var $db_type = 'mysql';
    var $date_type = DATE_DATETIME;
    var $db_timezone = 'UTC'; // A string timezone name.
    var $local_timezone = NULL; // A string timezone name.
    var $db_timezone_field = NULL; // Use if the db timezone is stored in a field.
    var $local_timezone_field = NULL; // Use if the local timezone is stored in a field.
    var $offset_field = NULL; // Use if the offset is stored in a field.

    function construct($date_type = DATE_DATETIME, $local_timezone = NULL) {
        $this->db_type = $GLOBALS['db_type'];
        $this->date_type = $date_type;
        $this->db_timezone = 'UTC';
        $this->local_timezone = isset($local_timezone) ? $local_timezone : date_default_timezone_name();
        if (isset($this->definition['content_field'])) {
            $this->date_handler->date_type = $this->definition['content_field']['type'];
        }
        date_api_set_db_timezone();
    }

    /**
     * See if the db has timezone name support.
     */
    function db_tz_support($reset = FALSE) {
        $has_support = variable_get('date_db_tz_support', -1);
        if ($has_support == -1 || $reset) {
            date_api_set_db_timezone();
            $has_support = FALSE;
            switch ($this->db_type) {
                case 'mysql':
                case 'mysqli':
                    if (version_compare(db_version(), '4.1.3', '>=')) {
                        $test = db_result(db_query("SELECT CONVERT_TZ('2008-02-15 12:00:00', 'UTC', 'US/Central')"));
                        if ($test == '2008-02-15 06:00:00') {
                            $has_support = TRUE;
                        }
                    }
                    break;
                case 'pgsql':
                    $test = db_result(db_query("SELECT '2008-02-15 12:00:00 UTC' AT TIME ZONE 'US/Central'"));
                    if ($test == '2008-02-15 06:00:00') {
                        $has_support = TRUE;
                    }
                    break;
            }
            variable_set('date_db_tz_support', $has_support);
        }
        return $has_support;
    }

    /**
     * Set the database timzone offset.
     *
     * Setting the db timezone to UTC is done to ensure consistency in date
     * handling whether or not the database can do proper timezone conversion.
     *
     * Views filters that not exposed are cached and won't set the timezone
     * so views date filters should add 'cacheable' => 'no' to their
     * definitions to ensure that the database timezone gets set properly
     * when the query is executed.
     *
     * @param $offset
     *   An offset value to set the database timezone to. This will only
     *   set a fixed offset, not a timezone, so any value other than
     *   '+00:00' should be used with caution.
     */
    function set_db_timezone($offset = '+00:00') {
        static $already_set = FALSE;
        $type = $GLOBALS['db_type'];
        if (!$already_set) {
            if (($type == 'mysqli' || $type == 'mysql') && version_compare(db_version(), '4.1.3', '>=')) {
                db_query("SET @@session.time_zone = '$offset'");
            } elseif ($type == 'pgsql') {
                db_query("SET TIME ZONE INTERVAL '$offset' HOUR TO MINUTE");
            }
            $already_set = TRUE;
        }
    }

    /**
     * Return timezone offset for the date being processed.
     */
    function get_offset() {
        if (!empty($this->db_timezone) && !empty($this->local_timezone)) {
            if ($this->db_timezone != $this->local_timezone) {
                $date = date_now($this->db_timezone);
                date_timezone_set($date, timezone_open($this->local_timezone));
                return date_offset_get($date);
            }
        }
        return 0;
    }

    /**
     * Helper function to create cross-database SQL dates.
     *
     * @param $field
     *   The real table and field name, like 'tablename.fieldname'.
     * @param $offset
     *   The name of a field that holds the timezone offset or an
     *   offset value. If NULL, the normal Drupal timezone handling
     *   will be used, if $offset = 0 no adjustment will be made.
     * @return
     *   An appropriate SQL string for the db type and field type.
     */
    function sql_field($field, $offset = NULL) {
        if (drupal_strtoupper($field) == 'NOW') {
            // NOW() will be in UTC since that is what we set the db timezone to.
            $this->local_timezone = 'UTC';
            return $this->sql_offset('NOW()', $offset);
        }
        switch ($this->db_type) {
            case 'mysql':
            case 'mysqli':
                switch ($this->date_type) {
                    case DATE_UNIX:
                        $field = "FROM_UNIXTIME($field)";
                        break;
                    case DATE_ISO:
                        if (version_compare(db_version(), '4.1.1', '>=')) {
                            $field = "STR_TO_DATE($field, '%Y-%m-%%dT%T')";
                        } else {
                            $field = "REPLACE($field, 'T', ' ')";
                        }
                        break;
                    case DATE_DATETIME:
                        break;
                }
                break;
            case 'pgsql':
                switch ($this->date_type) {
                    case DATE_UNIX:
                        $field = "$field::ABSTIME";
                        break;
                    case DATE_ISO:
                        $field = "TO_DATE($field, 'FMYYYY-FMMM-FMDDTFMHH24:FMMI:FMSS')";
                        break;
                    case DATE_DATETIME:
                        break;
                }
                break;
        }
        // Adjust the resulting value to the right timezone/offset.
        return $this->sql_tz($field, $offset);
    }

    /**
     * Adjust a field value by an offset in seconds.
     */
    function sql_offset($field, $offset = NULL) {
        if (!empty($offset)) {
            switch ($this->db_type) {
                case 'mysql':
                case 'mysqli':
                    if (version_compare(db_version(), '4.1.1', '>=')) {
                        return "ADDTIME($field, SEC_TO_TIME($offset))";
                    } else {
                        return "DATE_ADD($field, INTERVAL $offset SECOND)";
                    }
                case 'pgsql':
                    return "($field + INTERVAL '$offset SECONDS')";
                    ;
            }
        }
        return $field;
    }

    /**
     * Adjust a field value by time interval.
     *
     * @param $field
     *   The field to be adjusted.
     * @param $direction
     *   Either ADD or SUB.
     * @param $count
     *   The number of values to adjust.
     * @param $granularity
     *   The granularity of the adjustment, should be singular,
     *   like SECOND, MINUTE, DAY, HOUR.
     */
    function sql_date_math($field, $direction, $count, $granularity) {
        $granularity = drupal_strtoupper($granularity);
        switch ($this->db_type) {
            case 'mysql':
            case 'mysqli':
                switch ($direction) {
                    case 'ADD':
                        return "DATE_ADD($field, INTERVAL $count $granularity)";
                    case 'SUB':
                        return "DATE_SUB($field, INTERVAL $count $granularity)";
                }

            case 'pgsql':
                $granularity .= 'S';
                switch ($direction) {
                    case 'ADD':
                        return "($field + INTERVAL '$count $granularity')";
                    case 'SUB':
                        return "($field - INTERVAL '$count $granularity')";
                }
        }
        return $field;
    }

    /**
     * Select a date value from the database, adjusting the value
     * for the timezone.
     *
     * Check whether database timezone conversion is supported in
     * this system and use it if possible, otherwise use an
     * offset.
     *
     * @param $offset
     *   Set a fixed offset or offset field to use for the date.
     *   If set, no timezone conversion will be done and the
     *   offset will be used.
     */
    function sql_tz($field, $offset = NULL) {
        // If the timezones are values they need to be quoted, but
        // if they are field names they do not.
        $db_zone = $this->db_timezone_field ? $this->db_timezone_field : "'{$this->db_timezone}'";
        $localzone = $this->local_timezone_field ? $this->local_timezone_field : "'{$this->local_timezone}'";

        // If a fixed offset is required, use it.
        if ($offset !== NULL) {
            return $this->sql_offset($field, $offset);
        }
        // If the db and local timezones are the same, make no adjustment.
        elseif ($db_zone == $localzone) {
            return $this->sql_offset($field, 0);
        }
        // If the db has no timezone support, adjust by the offset,
        // could be either a field name or a value.
        elseif (!$this->db_tz_support()) {
            if (!empty($this->offset_field)) {
                return $this->sql_offset($field, $this->offset_field);
            } else {
                return $this->sql_offset($field, $this->get_offset());
            }
        }
        // Otherwise make a database timezone adjustment to the field.
        else {
            switch ($this->db_type) {
                case 'mysql':
                case 'mysqli':
                    return "CONVERT_TZ($field, $db_zone, $localzone)";
                case 'pgsql':
                    // WITH TIME ZONE assumes the date is using the system
                    // timezone, which should have been set to UTC.
                    return "$field::timestamp with time zone AT TIME ZONE $localzone";
            }
        }
    }

    /**
     * Helper function to create cross-database SQL date formatting.
     *
     * @param $format
     *   A format string for the result, like 'Y-m-d H:i:s'.
     * @param $field
     *   The real table and field name, like 'tablename.fieldname'.
     * @return
     *   An appropriate SQL string for the db type and field type.
     */
    function sql_format($format, $field) {
        switch ($this->db_type) {
            case 'mysql':
            case 'mysqli':
                $replace = array(
                    'Y' => '%Y', 'y' => '%y',
                    'm' => '%m', 'n' => '%c',
                    'd' => '%%d', 'j' => '%e',
                    'H' => '%H',
                    'i' => '%i',
                    's' => '%%s',
                    '\WW' => 'W%U',
                );
                $format = strtr($format, $replace);
                return "DATE_FORMAT($field, '$format')";
            case 'pgsql':
                $replace = array(
                    'Y' => 'YYYY', 'y' => 'Y',
                    'm' => 'MM', 'n' => 'M',
                    'd' => 'DD', 'j' => 'D',
                    'H' => 'HH24',
                    'i' => 'MI',
                    's' => 'SS',
                    '\T' => '"T"',
                        //'\W' => // TODO, what should this be?
                );
                $format = strtr($format, $replace);
                return "TO_CHAR($field, '$format')";
        }
    }

    /**
     * Helper function to create cross-database SQL date extraction.
     *
     * @param $extract_type
     *   The type of value to extract from the date, like 'MONTH'.
     * @param $field
     *   The real table and field name, like 'tablename.fieldname'.
     * @return
     *   An appropriate SQL string for the db type and field type.
     */
    function sql_extract($extract_type, $field) {
        // Note there is no space after FROM to avoid db_rewrite problems
        // see http://drupal.org/node/79904.
        switch (drupal_strtoupper($extract_type)) {
            case ('DATE'):
                return $field;
            case ('YEAR'):
                return "EXTRACT(YEAR FROM($field))";
            case ('MONTH'):
                return "EXTRACT(MONTH FROM($field))";
            case ('DAY'):
                return "EXTRACT(DAY FROM($field))";
            case ('HOUR'):
                return "EXTRACT(HOUR FROM($field))";
            case ('MINUTE'):
                return "EXTRACT(MINUTE FROM($field))";
            case ('SECOND'):
                return "EXTRACT(SECOND FROM($field))";
            case ('WEEK'):  // ISO week number for date
                switch ($this->db_type) {
                    case ('mysql'):
                    case ('mysqli'):
                        // WEEK using arg 3 in mysql should return the same value as postgres EXTRACT
                        return "WEEK($field, 3)";
                    case ('pgsql'):
                        return "EXTRACT(WEEK FROM($field))";
                }
            case ('DOW'):
                switch ($this->db_type) {
                    case ('mysql'):
                    case ('mysqli'):
                        // mysql returns 1 for Sunday through 7 for Saturday
                        // php date functions and postgres use 0 for Sunday and 6 for Saturday
                        return "INTEGER(DAYOFWEEK($field) - 1)";
                    case ('pgsql'):
                        return "EXTRACT(DOW FROM($field))";
                }
            case ('DOY'):
                switch ($this->db_type) {
                    case ('mysql'):
                    case ('mysqli'):
                        return "DAYOFYEAR($field)";
                    case ('pgsql'):
                        return "EXTRACT(DOY FROM($field))";
                }
        }
    }

    /**
     * Create a where clause to compare a complete date field to a complete date value.
     *
     * @param string $type
     *   The type of value we're comparing to, could be another field
     *   or a date value.
     * @param string $field
     *   The db table and field name, like "$table.$field".
     * @param string $operator
     *   The db comparison operator to use, like '='.
     * @param int $value
     *   The value to compare the extracted date part to, could be a
     *   field name or a date string or NOW().
     * @return
     *   SQL for the where clause for this operation.
     */
    function sql_where_date($type, $field, $operator, $value, $adjustment = NULL) {
        $type = drupal_strtoupper($type);
        if (drupal_strtoupper($value) == 'NOW') {
            $value = $this->sql_field('NOW', $adjustment);
        } elseif ($type == 'FIELD') {
            $value = $this->sql_field($value, $adjustment);
        } elseif ($type == 'DATE') {
            $date = date_make_date($value, date_default_timezone_name(), DATE_DATETIME);
            if (!empty($adjustment)) {
                date_modify($date, $adjustment . ' seconds');
            }
            // When comparing a field to a date we can avoid doing timezone
            // conversion by altering the comparison date to the db timezone.
            // This won't work if the timezone is a field instead of a value.
            if (empty($this->db_timezone_field) && empty($this->local_timezone_field) && $this->db_timezone_field != $this->local_timezone_field) {
                date_timezone_set($date, timezone_open($this->db_timezone));
                $this->local_timezone = $this->db_timezone;
            }
            $value = "'" . date_format_date($date, 'custom', DATE_FORMAT_DATETIME) . "'";
        }
        if ($this->local_timezone != $this->db_timezone) {
            $field = $this->sql_field($field);
        } else {
            $field = $this->sql_field($field, 0);
        }
        return "$field $operator $value";
    }

    /**
     * Create a where clause to compare an extracted part of a field to an integer value.
     *
     * @param string $part
     *   The part to extract, YEAR, MONTH, DAY, etc.
     * @param string $field
     *   The db table and field name, like "$table.$field".
     * @param string $operator
     *   The db comparison operator to use, like '='.
     * @param int $value
     *   The integer value to compare the extracted date part to.
     * @return
     *   SQL for the where clause for this operation.
     */
    function sql_where_extract($part, $field, $operator, $value, $adjustment = NULL) {
        $field = $this->sql_field($field, $adjustment);
        return $this->sql_extract($part, $field) . " $operator $value";
    }

    /**
     * Create a where clause to compare a formated field to a formated value.
     *
     * @param string $format
     *   The format to use on the date and the value when comparing them.
     * @param string $field
     *   The db table and field name, like "$table.$field".
     * @param string $operator
     *   The db comparison operator to use, like '='.
     * @param string $value
     *   The value to compare the extracted date part to, could be a
     *   field name or a date string or NOW().
     * @return
     *   SQL for the where clause for this operation.
     */
    function sql_where_format($format, $field, $operator, $value, $adjustment = NULL) {
        $field = $this->sql_field($field, $adjustment);
        return $this->sql_format($format, $field) . " $operator '$value'";
    }

    /**
     * An array of all date parts,
     * optionally limited to an array of allowed parts.
     */
    function date_parts($limit = NULL) {
        $parts = array(
            'year' => date_t('Year', 'datetime'), 'month' => date_t('Month', 'datetime'), 'day' => date_t('Day', 'datetime'),
            'hour' => date_t('Hour', 'datetime'), 'minute' => date_t('Minute', 'datetime'), 'second' => date_t('Second', 'datetime'),
        );
        if (!empty($limit)) {
            $last = FALSE;
            foreach ($parts as $key => $part) {
                if ($last) {
                    unset($parts[$key]);
                }
                if ($key == $limit) {
                    $last = TRUE;
                }
            }
        }
        return $parts;
    }

    /**
     * Part information.
     *
     * @param $op
     *   'min', 'max', 'format', 'sep', 'empty_now', 'empty_min', 'empty_max'.
     *   Returns all info if empty.
     * @param $part
     *   'year', 'month', 'day', 'hour', 'minute', or 'second.
     *   returns info for all parts if empty.
     */
    function part_info($op = NULL, $part = NULL) {
        $info = array();
        $info['min'] = array(
            'year' => 100, 'month' => 1, 'day' => 1,
            'hour' => 0, 'minute' => 0, 'second' => 0);
        $info['max'] = array(
            'year' => 4000, 'month' => 12, 'day' => 31,
            'hour' => 23, 'minute' => 59, 'second' => 59);
        $info['format'] = array(
            'year' => 'Y', 'month' => 'm', 'day' => 'd',
            'hour' => 'H', 'minute' => 'i', 'second' => 's');
        $info['sep'] = array(
            'year' => '', 'month' => '-', 'day' => '-',
            'hour' => ' ', 'minute' => ':', 'second' => ':');
        $info['empty_now'] = array(
            'year' => date('Y'), 'month' => date('m'), 'day' => min('28', date('d')),
            'hour' => date('H'), 'minute' => date('i'), 'second' => date('s'));
        $info['empty_min'] = array(
            'year' => '1000', 'month' => '01', 'day' => '01',
            'hour' => '00', 'minute' => '00', 'second' => '00');
        $info['empty_max'] = array(
            'year' => '9999', 'month' => '12', 'day' => '31',
            'hour' => '23', 'minute' => '59', 'second' => '59');
        if (!empty($op)) {
            if (!empty($part)) {
                return $info[$op][$part];
            } else {
                return $info[$op];
            }
        }
        return $info;
    }

    /**
     * Create a complete datetime value out of an
     * incomplete array of selected values.
     *
     * For example, array('year' => 2008, 'month' => 05) will fill
     * in the day, hour, minute and second with the earliest possible
     * values if type = 'min', the latest possible values if type = 'max',
     * and the current values if type = 'now'.
     */
    function complete_date($selected, $type = 'now') {
        if (empty($selected)) {
            return '';
        }
        // Special case for weeks.
        if (array_key_exists('week', $selected)) {
            $dates = date_week_range($selected['week'], $selected['year']);
            switch ($type) {
                case 'empty_now':
                case 'empty_min':
                case 'min':
                    return date_format($dates[0], 'Y-m-d H:i:s');
                case 'empty_max':
                case 'max':
                    return date_format($dates[1], 'Y-m-d H:i:s');
                default:
                    return;
            }
        }

        $compare = array_merge($this->part_info('empty_' . $type), $selected);
        // If this is a max date, make sure the last day of
        // the month is the right one for this date.
        if ($type == 'max') {
            $compare['day'] = date_days_in_month($compare['year'], $compare['month']);
        }
        $value = '';
        $separators = $this->part_info('sep');
        foreach ($this->date_parts() as $key => $name) {
            $value .= $separators[$key] . (!empty($selected[$key]) ? $selected[$key] : $compare[$key]);
        }
        return $value;
    }

    /**
     * Convert a format string into help text,
     * i.e. 'Y-m-d' becomes 'YYYY-MM-DD'.
     *
     * @param unknown_type $format
     * @return unknown
     */
    function format_help($format) {
        $replace = array(
            'Y' => 'YYYY', 'm' => 'MM', 'd' => 'DD',
            'H' => 'HH', 'i' => 'MM', 's' => 'SS', '\T' => 'T');
        return strtr($format, $replace);
    }

    /**
     *  A function to test the validity of various date parts
     */
    function part_is_valid($value, $type) {
        if (!preg_match('/^[0-9]*$/', $value)) {
            return FALSE;
        }
        $value = intval($value);
        if ($value <= 0)
            return FALSE;
        switch ($type) {
            case 'year':
                if ($value < DATE_MIN_YEAR)
                    return FALSE;
                break;
            case 'month':
                if ($value < 0 || $value > 12)
                    return FALSE;
                break;
            case 'day':
                if ($value < 0 || $value > 31)
                    return FALSE;
                break;
            case 'week':
                if ($value < 0 || $value > 53)
                    return FALSE;
        }
        return TRUE;
    }

    function views_formats($granularity, $type = 'sql') {
        $formats = array('display', 'sql');
        // Start with the site long date format and add seconds to it
        $long = str_replace(':i', ':i:s', variable_get('date_format_long', 'l, F j, Y - H:i'));
        switch ($granularity) {
            case ('year'):
                $formats['display'] = 'Y';
                $formats['sql'] = 'Y';
                break;
            case ('month'):
                $formats['display'] = date_limit_format($long, array('year', 'month'));
                $formats['sql'] = 'Y-m';
                break;
            case ('day'):
                $formats['display'] = date_limit_format($long, array('year', 'month', 'day'));
                $formats['sql'] = 'Y-m-d';
                break;
            case ('hour'):
                $formats['display'] = date_limit_format($long, array('year', 'month', 'day', 'hour'));
                $formats['sql'] = 'Y-m-d\TH';
                break;
            case ('minute'):
                $formats['display'] = date_limit_format($long, array('year', 'month', 'day', 'hour', 'minute'));
                $formats['sql'] = 'Y-m-d\TH:i';
                break;
            case ('second'):
                $formats['display'] = date_limit_format($long, array('year', 'month', 'day', 'hour', 'minute', 'second'));
                $formats['sql'] = 'Y-m-d\TH:i:s';
                break;
            case ('week'):
                $formats['display'] = 'F j Y (W)';
                $formats['sql'] = 'Y-\WW';
                break;
        }
        return $formats[$type];
    }

    function granularity_form($granularity) {
        $form = array(
            '#title' => t('Granularity'),
            '#type' => 'radios',
            '#default_value' => $granularity,
            '#options' => $this->date_parts(),
        );
        return $form;
    }

    /**
     * Parse date parts from an ISO date argument.
     *
     * Based on ISO 8601 date duration and time interval standards.
     *
     * See http://en.wikipedia.org/wiki/ISO_8601#Week_dates for definitions of ISO weeks.
     * See http://en.wikipedia.org/wiki/ISO_8601#Duration for definitions of ISO duration and time interval.
     *
     * Parses a value like 2006-01-01--2006-01-15, or 2006-W24, or @P1W.
     * Separate from and to dates or date and period with a double hyphen (--).
     *
     * The 'to' portion of the argument can be eliminated if it is the same as the 'from' portion.
     * Use @ instead of a date to substitute in the current date and time.
     *
     * Use periods (P1H, P1D, P1W, P1M, P1Y) to get next hour/day/week/month/year from now.
     * Use date before P sign to get next hour/day/week/month/year from that date.
     * Use period then date to get a period that ends on the date.
     *
     */
    function arg_parts($argument) {
        $values = array();
        // Keep mal-formed arguments from creating errors.
        if (empty($argument) || is_array($argument)) {
            return array('date' => array(), 'period' => array());
        }
        $fromto = explode('--', $argument);
        foreach ($fromto as $arg) {
            $parts = array();
            if ($arg == '@') {
                $parts['date'] = date_array(date_now());
            } elseif (preg_match('/(\d{4})?-?(W)?(\d{1,2})?-?(\d{1,2})?[T\s]?(\d{1,2})?:?(\d{1,2})?:?(\d{1,2})?/', $arg, $matches)) {
                $date = array();
                if (!empty($matches[1]))
                    $date['year'] = $matches[1];
                if (!empty($matches[3])) {
                    if (empty($matches[2])) {
                        $date['month'] = $matches[3];
                    } else {
                        $date['week'] = $matches[3];
                    }
                }
                if (!empty($matches[4]))
                    $date['day'] = $matches[4];
                if (!empty($matches[5]))
                    $date['hour'] = $matches[5];
                if (!empty($matches[6]))
                    $date['minute'] = $matches[6];
                if (!empty($matches[7]))
                    $date['second'] = $matches[7];
                $parts['date'] = $date;
            }
            if (preg_match('/^P(\d{1,4}[Y])?(\d{1,2}[M])?(\d{1,2}[W])?(\d{1,2}[D])?([T]{0,1})?(\d{1,2}[H])?(\d{1,2}[M])?(\d{1,2}[S])?/', $arg, $matches)) {
                $period = array();
                if (!empty($matches[1]))
                    $period['year'] = str_replace('Y', '', $matches[1]);
                if (!empty($matches[2]))
                    $period['month'] = str_replace('M', '', $matches[2]);
                if (!empty($matches[3]))
                    $period['week'] = str_replace('W', '', $matches[3]);
                if (!empty($matches[4]))
                    $period['day'] = str_replace('D', '', $matches[4]);
                if (!empty($matches[6]))
                    $period['hour'] = str_replace('H', '', $matches[6]);
                if (!empty($matches[7]))
                    $period['minute'] = str_replace('M', '', $matches[7]);
                if (!empty($matches[8]))
                    $period['second'] = str_replace('S', '', $matches[8]);
                $parts['period'] = $period;
            }
            $values[] = $parts;
        }
        return $values;
    }

    /**
     * Convert strings like '+1 day' to the ISO equivalent, like 'P1D'.
     */
    function arg_replace($arg) {
        if (!preg_match('/([+|-])\s?([0-9]{1,32})\s?([day(s)?|week(s)?|month(s)?|year(s)?|hour(s)?|minute(s)?|second(s)?]{1,10})/', $arg, $results)) {
            return str_replace('now', '@', $arg);
        }
        $direction = $results[1];
        $count = $results[2];
        $item = $results[3];

        $replace = array(
            'now' => '@',
            '+' => 'P',
            '-' => 'P-',
            'years' => 'Y',
            'year' => 'Y',
            'months' => 'M',
            'month' => 'M',
            'weeks' => 'W',
            'week' => 'W',
            'days' => 'D',
            'day' => 'D',
            'hours' => 'H',
            'hour' => 'H',
            'minutes' => 'M',
            'minute' => 'M',
            'seconds' => 'S',
            'second' => 'S',
            '  ' => '',
            ' ' => '',
        );
        $prefix = in_array($item, array('hours', 'hour', 'minutes', 'minute', 'seconds', 'second')) ? 'T' : '';
        return $prefix . strtr($direction, $replace) . $count . strtr($item, $replace);
    }

    /**
     * Use the parsed values from the ISO argument to determine the
     * granularity of this period.
     */
    function arg_granularity($arg) {
        $granularity = '';
        $parts = $this->arg_parts($arg);
        $date = !empty($parts[0]['date']) ? $parts[0]['date'] : (!empty($parts[1]['date']) ? $parts[1]['date'] : array());
        foreach ($date as $key => $part) {
            $granularity = $key;
        }
        return $granularity;
    }

    /**
     * Use the parsed values from the ISO argument to determine the
     * min and max date for this period.
     */
    function arg_range($arg) {
        // Parse the argument to get its parts
        $parts = $this->arg_parts($arg);

        // Build a range from a period-only argument (assumes the min date is now.)
        if (empty($parts[0]['date']) && !empty($parts[0]['period']) && (empty($parts[1]))) {
            $min_date = date_now();
            $max_date = drupal_clone($min_date);
            foreach ($parts[0]['period'] as $part => $value) {
                date_modify($max_date, "+$value $part");
            }
            date_modify($max_date, '-1 second');
            return array($min_date, $max_date);
        }
        // Build a range from a period to period argument
        if (empty($parts[0]['date']) && !empty($parts[0]['period']) && !empty($parts[1]['period'])) {
            $min_date = date_now();
            $max_date = drupal_clone($min_date);
            foreach ($parts[0]['period'] as $part => $value) {
                date_modify($min_date, "+$value $part");
            }
            date_modify($min_date, '-1 second');
            foreach ($parts[1]['period'] as $part => $value) {
                date_modify($max_date, "+$value $part");
            }
            date_modify($max_date, '-1 second');
            return array($min_date, $max_date);
        }
        if (!empty($parts[0]['date'])) {
            $value = date_fuzzy_datetime($this->complete_date($parts[0]['date'], 'min'));
            $min_date = date_make_date($value, date_default_timezone_name(), DATE_ISO);
            // Build a range from a single date-only argument.
            if (empty($parts[1]) || (empty($parts[1]['date']) && empty($parts[1]['period']))) {
                $value = date_fuzzy_datetime($this->complete_date($parts[0]['date'], 'max'));
                $max_date = date_make_date($value, date_default_timezone_name(), DATE_ISO);
                return array($min_date, $max_date);
            }
            // Build a range from start date + period.
            elseif (!empty($parts[1]['period'])) {
                foreach ($parts[1]['period'] as $part => $value) {
                    $max_date = drupal_clone($min_date);
                    date_modify($max_date, "+$value $part");
                }
                date_modify($max_date, '-1 second');
                return array($min_date, $max_date);
            }
        }
        // Build a range from start date and end date.
        if (!empty($parts[1]['date'])) {
            $value = date_fuzzy_datetime($this->complete_date($parts[1]['date'], 'max'));
            $max_date = date_make_date($value, date_default_timezone_name(), DATE_ISO);
            if (isset($min_date)) {
                return array($min_date, $max_date);
            }
        }
        // Build a range from period + end date.
        if (!empty($parts[0]['period'])) {
            $min_date = date_now();
            foreach ($parts[0]['period'] as $part => $value) {
                date_modify($min_date, "$value $part");
            }
            return array($min_date, $max_date);
        }
        // Intercept invalid info and fall back to the current date.
        $now = date_now();
        return array($now, $now);
    }

}